Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.77	7.804%	$187.331	$187.33	$187.35	$187.30
Purchase #2	$9.78	5.369%	$10.3051	$10.31	$10.30	$10.30
Purchase #3	$33.86	12.722%	$38.1677	$38.17	$38.15	$38.20
Purchase #4	$51.55	6.341%	$54.8188	$54.82	$54.80	$54.80
Purchase #5	$220.97	8.215%	$239.1227	$239.12	$239.10	$239.10
Purchase #6	$140.96	10.860%	$156.2683	$156.27	$156.25	$156.30
Purchase #7	$161.46	3.795%	$167.5874	$167.59	$167.60	$167.60
7 purchase totals =	$792.35		$853.6010	$853.61	$853.55	$853.60